CN106321317B

CN106321317B - Method for determining operating parameters of a fuel pump

Info

Publication number: CN106321317B
Application number: CN201610491638.9A
Authority: CN
Inventors: H.赫梅斯; F.施米特; U.福尔奇; U.舒尔兹; T.弗里伊德; U.米勒; M.斯特拉斯塞; A.珍内
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2015-06-30
Filing date: 2016-06-29
Publication date: 2020-08-11
Anticipated expiration: 2036-06-29
Also published as: CN106321317A; DE102015212121A1

Abstract

The invention relates to a method for adjusting at least one operating parameter of an electric fuel pump (120) which is connected to a fuel circuit (140) having a spill valve (133), wherein a pressure is built up in the fuel circuit (140) by means of the electric fuel pump (120) at least until an opening pressure (p') of the spill valve (133) is reached, and wherein the at least one operating parameter is adjusted on the fuel circuit (140) while taking into account at least one value of the at least one operating parameter which corresponds to the opening pressure of the spill valve (133).

Description

Method for determining operating parameters of a fuel pump

Technical Field

The present invention relates to a method for determining at least one operating parameter of an electric fuel pump, as well as to a computing unit and a computer program for carrying out the method.

Background

In modern motor vehicles with internal combustion engines, one or more electric fuel pumps are mostly used in the low-pressure fuel system, i.e. in the low-pressure region of the fuel Supply, in particular in the form of so-called Pre-Supply pumps (Pre-Supply Pump in english), whereby fuel is delivered from a fuel tank to a high-pressure Pump.

The advantage of the rapid availability of the fuel pre-supply by the electric fuel pump at start-up is thereby combined with the advantage of the hydraulic efficiency of the fuel pump driven by the internal combustion engine. Furthermore, the fuel supply can be carried out as required. Electric fuel pumps require their own control or regulating mechanism and for this purpose have electronic devices which can be integrated into the fuel pump, for example.

Since such electric fuel pumps can be controlled or regulated in terms of their delivery pressure and their delivery volume (delivery volume), adaptation to the respective operating environment can often be meaningful or desirable.

Disclosure of Invention

According to the invention, a method for adjusting at least one operating parameter of an electric fuel pump is proposed, as well as a computing unit and a computer program for carrying out the method. In a method for determining at least one operating parameter of an electric fuel pump, which is connected to a fuel circuit having a spill valve, a pressure is built up in the fuel circuit by means of the electric fuel pump at least until an opening pressure of the spill valve is reached, and at least one operating parameter is determined taking into account at least one value of the at least one operating parameter which corresponds to the opening pressure of the spill valve, wherein the at least one operating parameter comprises a current and/or a rotational speed of the electric fuel pump. The computing unit is provided for carrying out the method. A machine-readable storage medium has stored thereon a computer program which, when executed on a computing unit, causes the computing unit to carry out the method. Advantageous embodiments are the contents of the following description.

THE ADVANTAGES OF THE PRESENT INVENTION

The method according to the invention is used to determine at least one operating parameter of an electric fuel pump which is connected to a fuel circuit having a spill valve, in particular a low-pressure fuel circuit. In this case, a pressure is built up in the fuel circuit by means of the electric fuel pump at least until the opening pressure of the overflow valve is reached, and at least one operating parameter is determined taking into account at least one value of the at least one operating parameter which corresponds to the opening pressure of the overflow valve.

A relief valve is provided in a low-pressure fuel circuit of a motor vehicle to limit the pressure in the low-pressure fuel circuit. For this purpose, the overflow valve has a preset and known opening pressure, from which the overflow valve opens. In particular in the case in which the high-pressure fuel circuit connected to the low-pressure fuel circuit should not or does not have to be supplied by the low-pressure fuel circuit, for example because the internal combustion engine is not in operation, the pressure in the low-pressure fuel circuit generally rises excessively. In addition, such relief valves usually have an outflow channel which is also open during normal operation, so that a small volume flow is guided past the high-pressure fuel circuit (bypass), for example for cooling the components involved.

If the pressure in the fuel circuit is now built up by means of the electric fuel pump and at least until the known opening pressure of the overflow valve is reached, a relationship between the delivery pressure of the fuel pump and the operating parameters can be built up as a function of the operating parameters, in particular the current and/or the rotational speed, which are required for operating the electric fuel pump at the point in time when the opening pressure is reached (which may be 3bar, for example). It goes without saying that corresponding parameters need to be determined for this purpose, but this can generally be achieved without problems by means of an existing pump controller. In particular, values in which the fuel pump is not operated, i.e., for example, no current is present at a pressure of 0bar, can also be considered for this purpose. To this end, it is to be mentioned that the characteristic of an electric fuel pump is generally linear in this relationship. But in addition the offset of the fuel pump can also be taken into account in this way.

In this way, for example, in the event of a replacement of the fuel pump, a simple and rapid determination of the operating parameters of a new fuel pump can be carried out, i.e., for example, a relationship can be established between the current and the rotational speed of the fuel pump on the one hand and the pressure and/or volume flow generated, which is typical, in particular, for the fuel circuit, on the other hand. This is generally required because there may be variations due to manufacturing tolerances even in the same type of fuel pump. Furthermore, other types of fuel pumps may be used as alternatives in this manner. The fuel pump may be, for example, an electric gear pump or an electric roller vane pump (rotary pump).

Preferably, the at least one operating parameter is determined taking into account at least one value of the at least one operating parameter which corresponds to a volume flow through the relief valve before, during and/or after the opening pressure is reached. As already mentioned, relief valves generally have an outflow channel which is always open. This means that even with a closed overflow valve, a very small volume flow is possible, for example 20 l per h and bar. In contrast, after opening, there can be significantly larger volume flows, for example 400 l per h and bar. A more precise determination of the operating parameter can thereby be carried out.

Advantageously, the pressure in the fuel circuit is built up during the period in which no fuel is fed via the fuel circuit into a further fuel circuit, in particular a high-pressure fuel circuit, connected thereto and/or during the period in which an internal combustion engine, which is fed at least indirectly via the fuel circuit, in particular via the further fuel circuit, is not in operation. This ensures that the pressure exerted by the fuel pump also corresponds to the pressure exerted on the overflow valve. By means of a suitable control by the pump and/or the engine control unit, it can be ensured, for example, that the determination of the operating parameters of the fuel pump is carried out only in the case of an inactive internal combustion engine.

Advantageously, the leakage of the fuel circuit is also determined by comparing the measured value of the volume flow in the fuel circuit with the value of the volume flow typical for a spill valve. For this purpose, for example, the volume flow/pressure change in the fuel circuit can be measured and subtracted from this, which is typical and known for relief valves. The leakage in the fuel circuit can thus be determined very simply.

Preferably, the measured values and the values typical for a relief valve for the volume flow are taken into account before and after the opening pressure of the relief valve is reached. In particular, a plurality of measuring points can be used overall in order to obtain as precise a result as possible.

Advantageously, the leakage of the fuel circuit is taken into account when determining the at least one operating parameter. This makes it possible to determine the operating parameters of the fuel pump more precisely and thus to adapt the fuel circuit.

Advantageously, the determination of the at least one operating parameter is carried out after the replacement of the electric fuel pump and/or after a predetermined, in particular periodic, time interval, respectively. In the former case, a new fuel pump can thus be quickly and easily adjusted, which is used, for example, as a replacement for a defective, old fuel pump. This can be carried out, for example, in particular automatically, wherein a pump controller, for example, a new fuel pump, informs the higher-level engine controller that the new pump has not yet been set and that setting is subsequently carried out. In the latter case, the pump that has been used can be adapted to the conditions that may change, for example leakage due to ageing. The determination of the operating parameters can in this case be carried out, for example, before each or every fifth or tenth start of the internal combustion engine. However, the interval can also be selected to be shorter, for example, with increasing operating duration of the fuel pump and/or the fuel circuit.

Preferably, the at least one operating parameter is stored in a non-volatile memory after the determination, in particular in the pump controller, for a further operation of the electric fuel pump. This makes it possible to control the fuel pump easily and appropriately in normal operation.

A computing unit according to the invention, for example a control unit of a motor vehicle, is provided, in particular in a program-technical manner, for carrying out the method according to the invention. Such a control device is in particular the already mentioned pump control device of the fuel pump or the engine control device, which is usually arranged in an upper position with respect to the pump control device and is connected to the latter for data exchange.

The implementation of the method in the form of a computer program is also advantageous, since this entails little expenditure, in particular if the controller that is executed is also used for other tasks and is therefore present anyway. Suitable data carriers for supplying the computer program are, in particular, magnetic, optical or electrical memories, for example hard disks, flash memories, EEPROMs, DVDs etc. It is also possible to download the program via a computer network (internet, intranet, etc.).

Further advantages and embodiments of the invention will appear from the description and the drawings.

The invention is schematically illustrated in the drawings by means of embodiments and described below with reference to the drawings.

Drawings

Fig. 1 schematically shows a part of a fuel supply system with an electric fuel pump, in which the method according to the invention can be implemented.

Fig. 2 shows a typical volume flow-pressure-change curve for a relief valve.

Fig. 3 shows a block diagram schematically illustrating the flow of the method according to the invention in a preferred embodiment.

Detailed Description

Fig. 1 shows schematically and by way of example a part of a fuel supply system 100 of an internal combustion engine of a motor vehicle having an electric fuel pump 120, in which a method according to the invention can be carried out. Here, fuel is delivered from a fuel tank 110 by means of a fuel pump 120 via two

filters

111 and 112 to a high-pressure pump 130.

In the high-pressure pump 130 comprised by the other fuel circuit constituted by the high-pressure fuel circuit 145, fuel is fed to the two pistons 135 arranged in the drive mechanism chamber 132 via the quantity regulator 131 and the two inlet valves 136. The two pistons 135 are coupled to and driven by an internal combustion engine 150. Via the outlet valve 137, fuel can be supplied to a high-pressure accumulator (not shown here), for example.

Furthermore, an overflow valve 133 is shown, as well as, for example, two bearing

leaks

134 and 138, via which fuel is returned into the fuel tank 110. By means of the overflow valve 133, the fuel can flow permanently via a small outflow channel at a small volume flow, for example for cooling the high-pressure pump 130, and at a large volume flow in the open state.

The fuel pump 120 is a pre-supply pump (primary fuel pump) operated by means of an electric motor, which is located in a low-pressure fuel circuit 140 of the fuel supply system 100. The low-pressure fuel circuit 140 includes the fuel tank 110, the

filters

111, 112, the fuel pump 120, and the spill valve 133. For the sake of completeness, it should be pointed out that the low-pressure fuel circuit 140 may also be led partially through the housing of the high-pressure pump 130, for example in order to cool it. The fuel pump 120 may be, for example, an electrically operated gear pump.

The fuel pump 120 is assigned a pump controller 170 which is provided for controlling and/or regulating the fuel pump 120 and has corresponding equipment, for example a microprocessor, measuring technology and suitable software, for this purpose. In particular, the current applied or flowing during operation of the fuel pump 120 can be detected by means of measurement technology.

Furthermore, an engine controller 180 is provided, to which the pump controller 170 is connected in a data-transmitting manner. The engine controller 180, during control of the internal combustion engine, which is supplied with fuel via the fuel supply system 100, sends a corresponding command, such as a rotation speed or a volume flow rate, to the pump controller 170 to control the fuel pump 120 as desired.

A typical volume flow/pressure curve f for a relief valve is shown by way of example in fig. 2. Here, the volume flow is given in l/h (liters per hour)

The pressure difference △ p is plotted against the pressure difference in bar, which here corresponds to the pressure difference of the pressures before and after the overflow valve.

It can be seen in the variation curve f that its gradient is initially small, approximately 20 l/(h.bar), and that, starting from a pressure p' ≈ 3bar, which corresponds to the opening pressure of the relief valve, the gradient becomes significantly greater, approximately 400 l/(h.bar). Relief valves have such or similar profiles, which are also generally known.

If, for example, a new electric fuel pump is now installed in a low-pressure fuel circuit, the determination of the operating parameters of the new fuel pump can be carried out. Preferably, the fuel pump is then operated using the determined operating parameters.

Fig. 3 schematically shows a block diagram of a method according to the invention in a preferred embodiment.

For this purpose, in step 310, after it is ensured that the internal combustion engine is not in operation and therefore no fuel is fed from the low-pressure fuel circuit into the high-pressure fuel circuit, it is possible to measure the volumetric flow rate/pressure change in the low-pressure fuel circuit in step 300.

For this purpose, the fuel pump can be operated in such a way that the pressure and the volume flow provided by the fuel pump increase continuously. In this way, a variation curve f' as can be seen in fig. 2 can be obtained. The curve f' corresponds here to the curve f of the relief valve plus a possible leakage. In contrast, the value of the opening pressure p' does not change relative to the curve f. Instead of the entire profile f ', it is also possible here to measure only a part of this profile around an opening pressure p' known per se.

Thus, a conversion between the operating parameter and the pressure or the volume flow can be carried out in step 320 from the values of the operating parameter at the time of reaching the opening pressure, i.e. in particular the current and the rotational speed. The ratio between the pressure and the current or between the volume flow and the rotational speed of the fuel pump is in this case generally proportional to one another. To this end, the volume flow through the overflow valve is also known.

In addition, in step 330, the leakage quantity can be determined from a comparison of the characteristic curves f' and f, in particular also with the aid of a pressure dependency. This can be taken into account when determining the operating parameters.

The determination of the operating parameters and thus the adaptation to the low-pressure fuel circuit can now be carried out in step 340 and the operating parameters can be stored, for example, in a memory of the pump controller.

Claims

1. Method for determining at least one operating parameter of an electric fuel pump (120) which is connected to a fuel circuit (140) having a spill valve (133),

wherein a pressure is built up in the fuel circuit (140) by means of the electric fuel pump (120) at least until an opening pressure (p') of the overflow valve (133) is reached, and

wherein at least one operating parameter is determined taking into account at least one value of the at least one operating parameter corresponding to the opening pressure (p') of the spill valve (133), wherein the at least one operating parameter comprises the current and/or the rotational speed of the electric fuel pump (120).

2. A method according to claim 1, wherein the at least one operating parameter is determined taking into account at least one value of the at least one operating parameter corresponding to a volume flow through the spill valve (133) before, during and/or after the opening pressure (p') is reached.

3. Method according to claim 1 or 2, wherein the pressure in the fuel circuit (140) is built up during periods when no fuel is being delivered via the fuel circuit (140) into another fuel circuit (145) connected thereto and/or during periods when an internal combustion engine (150) which is being supplied at least indirectly via the fuel circuit (140) is not in operation.

4. A method according to claim 3, wherein during periods when the internal combustion engine (150) fed via the further fuel circuit (145) is not in operation, pressure in the fuel circuit (140) is established.

5. A method according to claim 1 or 2, wherein the leakage of the fuel circuit (140) is determined by comparing a measured value of the volume flow in the fuel circuit (140) with a value of the volume flow typical for the spill valve (133).

6. Method according to claim 5, wherein in the measured values and in the values typical for the volume flow for the overflow valve (133), the values before and after the opening pressure (p') of the overflow valve (133) are taken into account.

7. The method of claim 5, wherein an amount of leakage of the fuel circuit (140) is taken into account when determining the at least one operating parameter.

8. Method according to claim 1 or 2, wherein the determination of the at least one operating parameter is carried out after a replacement of the electric fuel pump (120) and/or after a predetermined time interval, respectively.

9. A method according to claim 1 or 2, wherein at least one operating parameter is stored in a non-volatile memory after the determination for another operation of the electric fuel pump.

10. The method according to claim 8, wherein the determination of the at least one operating parameter is carried out after a regular time interval, respectively.

11. A computing unit (170, 180) arranged for implementing the method according to any one of claims 1 to 10.

12. A machine-readable storage medium having stored thereon a computer program which, when executed on a computing unit (170, 180), causes the computing unit (170, 180) to carry out the method according to any one of claims 1 to 10.